Method of inhibiting the oxidation and hydration of lead alloys



Patented Qct. 25, 1932 UNITED STATES PATENT OFF-ICE EDGAR W. FIELDING,OF WILMINGTON, DELAWARE, ASSIGNOR TO E. I. DU PONT DE NEMOURS & COMPANY,OF WILMINGTON, DELAWARE, A CORPORATION, OF DELA- WARE METHOD OFINHIBITING THE OXIDATION AND HYDRATION OF LEAD ALLOYS No Drawing.

This invention relates to a method of preventing the oxidationnndhydration of leadsodium alloys, and particularly to such alloys intendedfor use in the manufacture of tetraalkyl-lead.

- It has heretofore been the practice in making alloys of lead andsodium to discharge such alloys from the melting pots in which they aremade into suitable receptacles holding approximately 500 pounds ofalloy, and in which the alloy is cooled. The practice of dischargingmaterial in this manner, however, is accompanied by certaindisadvantages in that considerable oxidation and hydration occurs, bothwhile the stream of molten alloy is flowing from the alloy pot into themold, as Well as on the surface of the mold during the cooling period.Such a con dition tends to destroy the value of lead-sodium alloy whenit is employed for certain subsequent purposes, and particularly for theproduction of tetra-alkyl-lead, and especially tetra-ethyl-lead, orother organo lead derivatives.

An object of the present invention is to overcome the oxidation andhydration of molten lead sodium alloys. A further object is to improvegenerally upon the condition of lead alloys. pear hereinafter.

These objects are accomplished by the following invention in which Ihavefound that the oxidation and hydration of lead sodium alloys can beovercome by the addition of a small quantity of mineral oil to the alloymold prior to the casting of the charge from the alloy pot. While thequantity and character of the oil may vary within rather wide limits, 1preferablyadd approximately one .40 pint of a high-flash mineral oil.The beneficial efiect to be derived from the use of such an oil appearsto reside in the fact that when the hot alloy strikes the oil as thealloy flows into the bottom of the mold, part of the oil is vaporizedand surrounds the stream of Application filed ihiarch 28, 1931.

Uther objects will ap Serial No. 526,142.

molten alloy, thus providing a reducing atmosphere which tends toblanket the stream of hot alloy from contact with the air. When the moldis full the oil floats on the surface of the mold and covers the alloywith a protective film.

Other methods of producing an atmosphere of the vapors of the oil willbe apparent but I have foundthe foregoing to be convenient andsatisfactory.

l have found that this procedure results in a very material advantage,in that little or no reaction with air occurs during the casting andcooling period, and as a result higher yields of tetra-alkyl-lead, andparticularly tetra-ethyl-lead, may be obtained when the alloy is usedfor the purpose of producing tetra-ethyl-lead by reaction with ethylchloride or other organo derivatives by reaction with alkyl or arylhalides.

With the view of more clearly defining my invention the followingillustrative example of one embodiment thereof is given, but

it is to be understood that the scope of my invention is to be limitedonly'as indicated by the patent claims appearing hereinafter:

EwampZe:-A lead sodium alloy is prepared in a regulation alloy pot inthe usual manner known in the art. When this alloy has been prepared itis cast into cones-having a capacity of approximately 500 pounds andwhich have been previously treated by the addition of one pint of summerblack oil such as is used for the lubrication of the journal boxes onrailway cars. been cast, it is set aside to cool and solidify.

Other oils which have high flash points, and especially those havingflash points above 300 C. may be used for this purpose.

I claim: r

l. The process of inhibiting the oxidation and hydration of a hot leadsodium alloy which comprises maintaining an atmosphere of the vapors ofa mineral oil having a flash point above 300 C. in contact with thealloy.

When the alloy has 2. The process of inhibiting the oxidation andhydration of a hot lead sodium alloy which comprises enveloping thealloy in an atmosphere of the vapors of a mineral oil having a flashpoint above 300 (1 3. In the molding of lead alloys the method ofinhibiting the oxidation and hydration of the hot alloys which comprisessaturating the inner surfaces of the mold with a mineral oil having aflash point above 300 C. and which Will vaporize at least partially atthe melting temperature of the alloy.

4. The method of molding lead alloys and simultaneously inhbitingoxidation and hydration thereof Which comprises pouring molten alloyinto a mold containing a mineral oil having a flash point above 300 C.and

vaporizing at least partially at the melting a temperature of the alloy,the" oil be ng in sufiicient amount to form vapors enveloping the streamof alloy during the pouring and to form an oil layer above the castingWhen the mold is filled.

5. The method of molding lead alloys and simultaneouslyinhibitingoxidation and hydration thereof which comprises pouring moltenalloy into a mold containing summer black oil sufficient in amount toform vapors enveloping the stream of alloy during the pouring and toform an oil layer on the top of the casting when the mold is filled.

In testimony whereof I aifix my signature.

EDGAR W. FIELDING.

